Boom sections of telescopic cranes can comprise an upper shell and a lower shell that can be connected by means of a weld seam extending over the whole length of the section. These upper and lower shells can themselves already comprise a plurality of metal sheets, with fitting edges being able to extend both transversely and longitudinally with respect to the boom section. This type of construction is characterized in that the components of the upper shell and lower shell are produced from rectangular metal sheets and in that the connecting weld seam or the connecting weld seams of the upper and lower shells extend in parallel with the section edges of the boom section. This is related to the fact that non-planar regions of the boom section or of the upper shell and of the lower shell can be connected to one another with difficulty.
It is disadvantageous with the boom sections known from the prior art that the lower and upper shells welded to one another in parallel with their section edges have a constant lateral cross-section along the total length of the boom section or along a part of the boom section (e.g., only part of the boom section) while the load introduced into the boom section varies in dependence on the position at the boom section and on the force acting overall on the boom.
Known boom sections thereby have overdimensioned lateral cross-section portions in some regions while the same lateral cross-section portions can be underdimensioned in other regions of the boom section for correspondingly larger torques that occur there. It is known in a disadvantageous manner in this respect for the secure and stable design of the boom sections to design them such that the strength of the lower and upper shells is dimensioned to be sufficiently large along the total section length for the taking up of the largest torque occurring at the boom section. This has the result that a considerable overdimensioning of the boom section occurs in regions of the boom section having smaller loads introduced and thus an unnecessary large amount of material is installed and correspondingly excessive costs and weight arise in the manufacturing of corresponding boom sections.
Against this background, it is the object of the present disclosure to provide a boom section that is better adapted to the loads of different amounts that occur along the boom section and that can in this respect be manufactured with less use of material.
This object is achieved in accordance with the present disclosure by a boom section having a lower shell and an upper shell, wherein the lower shell and the upper shell are welded to one another, and wherein the weld seam extends between the lower shell and the upper shell angled in at least one region to at least one section edge of the boom section.
The angled extent of the weld seam in this respect means an extent that is not in parallel with the section edges. It is possible by the angled arrangement of the weld seam or of the weld seams between the lower shell and the upper shell to manufacture the lower shell and the upper shell of components that do not have any constant dimensions along the longitudinal axis of the boom section. A lower shell of optionally thicker design can thus, for example, take up a larger region of the cross-section of the boom section (referring to a lateral cross-section perpendicular to the longitudinal direction) in regions in which large loads act on the lower shell of the boom section, while the stronger or thicker lower shell can take up a smaller portion of the lateral cross-section of the boom section in regions of the boom section in which smaller loads act on the boom section or on its lower shell.
In these regions, in contrast, an upper shell that is thinner than the lower shell can take up a larger portion of the lateral cross-section of the boom section. A correspondingly obliquely extending weld seam or correspondingly obliquely extending weld seams thus enable boom sections to be manufactured with heterogeneous mechanical properties along the section length that are adapted to different load scenarios occurring along their longitudinal axes. The amount of material for providing a boom section having a defined stiffness can hereby be reduced. Conversely, the permissible payload of the corresponding telescopic boom can be increased with the same material use.
The term section edges can in this respect include all non-planar structures of the boom section, for example substantially longitudinally extending edges or correspondingly extending bending edges of the boom section. The boom section can in this respect have a polygonal and/or rounded lateral cross-sectional surface perpendicular to the longitudinal direction of the boom section. The external outlines of the lateral cross-sectional surface of the boom section can be polygonal and/or rounded, for example, due to the presence of the section edges between the planar portions of the boom section. In particular, where a cross-sectional view shows bent features, “section edges” may refer to areas where a bent structure meets a planar structure.
The “section edges” may be any edges of each of the upper shell and the lower shell. Section edges of the upper shell may be structurally integral with and formed from the same material as the remaining portions of the upper shell, and section edges of the lower shell may be structurally integral with and formed from the same material as the remainder of the lower shell.
The term weld seam is not related in the present case in a restrictive manner to a single weld seam between the lower shell and the upper shell; a plurality of weld seams, e.g. two weld seams, can also be present. They can be arranged at oppositely disposed sides of the boom section and can in particular extend symmetrically to one another. In other examples, there may be three, four, five, or more weld seams between the lower shell and the upper shell.
It is conceivable in an embodiment of the present disclosure that the lower shell has a greater thickness than the upper shell. Higher compression forces occurring at the thicker lower shell or bending torques that vary along the length of the boom section can thus advantageously be taken up by the lower shell without the lower shell in this respect being overdimensioned in portions for the correspondingly occurring loads and without thereby an overdimensioned boom section being present overall.
It is furthermore conceivable in a further embodiment that the lower shell rises in accordance with the torque progression (e.g., torque path) in the boom section. The rising of the lower shell in this respect means that it adopts a larger cross-sectional portion of the lateral cross-section of the boom section from bottom to top on an observation of the boom section from the side. If, for example, a linear increase of the load or of the introduced torque occurs at the boom section in question, the weld seam can rise in a correspondingly linear manner along the boom section.
It is conceivable in a further embodiment that the weld seam between the lower shell and the upper shell extends along the whole boom section (e.g., along the entire length of the boom section in the longitudinal direction) at a constant angle or at a varying angle to the section edges of the boom section and/or in a curved manner. The constant angle may be an angle greater than 0 degrees (e.g., such that the weld seam is not parallel to the section edge(s). Similar, each variation of the varying angle may be greater than 0 degrees. It is alternatively also conceivable that the weld seam between the lower shell and the upper shell extends along a part of the length of the boom section at a constant angle greater than 0 degrees or at a varying angle greater than 0 degrees to the section edges of the boom section and/or in a curved manner. The weld seam between the lower shell and the upper shell can extend in parallel with the section edges of the boom section along a different part or different parts of the boom section. Freely or approximately freely extending weld seam extents are also conceivable that make it possible to respond in a simple construction manner to structures such as bolting elements or other load introductions at the boom section. Mounts for these structures can be configured as reinforced by means of a lower shell that has larger dimensions and/or that takes up a larger part of the lateral cross-section of the boom section. The edges of the lower shell and of the upper shell are produced such that they correspond to one another or can be welded to one another without gaps when placed next to one another. For this purpose, an edge of a lower shell can be formed as a negative of the edge of an upper shell welded to it. This applies equally to weld seams that extend in angled form and in parallel and/or curved with respect to the section edges of the boom section.
It is furthermore conceivable in an embodiment that the lower shell and the upper shell are welded to one another in a laser hybrid process. Such methods make it possible to establish weld seams not extending in a planar manner simply, whereby welding can take place correspondingly over bending edges of the boom section extending longitudinally or at an angle. Alternatively or additionally, other welding processes are also conceivable by means of which a corresponding non-planar weld seam can be manufactured automatically.
The present disclosure furthermore relates to a boom for a telescopic crane having at least one of the boom sections described herein, as well as to a telescopic crane having at least one of the boom sections described herein.
Further details and advantages of the present disclosure are shown with reference to exemplary embodiments shown in the Figures.